Integrated circuit dies may be attached to substrates, circuit boards, or other dies using a process commonly referred to in the art as thermal compression bonding. Solder balls may be attached to various points of the die that are desired to be anchored to the substrate. The die may then be heated to melt the solder balls. The die and substrate may then be compressed such that, when the solder balls cool, the die may be attached to the substrate. A thermal compression bonding (TCB) process bond head may include a heater used during a fabrication process to heat the die, substrate, and solder balls in order to perform the bonding.
FIG. 1 illustrates a typical stack of a memory die 100, a logic die 101, and a substrate 102 that may be bonded using a TCB process. TCB may be used for attaching the memory die 100 to the logic die 101 with through silicon vias at a joint that may commonly be referred to as a logic-to-memory interconnect (LMI) joint 110. TCB may also be used in a first level interconnect (FLI) joint 111 between the logic die 101 and the substrate 102. The LMI joint 110 height may be very small compared to the FLI joint 111 height. For example, the LMI joint 110 height might be around 5 μm while the FLI joint 111 height might be around 50 μm. Thus, the positioning of the memory and logic dies 100, 101 during the TCB process should be very accurate to avoid bonding and joint problems.
One problem that may occur with the present TCB process is that, as the heater temperature increases, the TCB head may expand. Downward expansion of the head may cause the LMI joint height to become even smaller. This may result in solder ball bridging, resulting in shorting together of interconnects, and/or cracks in the dies 100, 101.
There are general needs for better control of joint heights during a thermal compression bonding process.